System for delineating selective response of a material to radiation in presence of visible illumination

ABSTRACT

A pulsed visible illumination source illuminates a material to allow, for example, a helicopter pilot to fly over the surface of the earth in darkness. The visible light is interrupted to allow a pulsed ultraviolet source to stimulate luminescent reradiation from the material which reradiation is detected by observers and/or cameras. Both observers and camera are shielded by goggles or shutters so that the stimulated luminescence produced by the ultraviolet is not masked by the visible illumination. Such shutters are synchronized with the visible illumination pulses.

United States Patent Madsen 1 Ma 16 1972 54] SYSTEM FOR DELINEATING3,305,089 2/1967 Fraenkel ..250/71 x SELECTIVE RESPONSE OF A 3,444,5175/1969 Rabinow.. ...250/7l X 3,501,639 3/1970 MOI'IIOC ..250/71 XPRESENCE OF VISIBLE OTHER PUBLICATIONS ILLUMINATION Brown, Review ofScientific Instruments Vol. 34 Number 4, [72] Inventor: Andrew Madsen,Alamo, C lif" Simplified System for the Measurement of FluorescenceLifetimes Using the Stroboscopic Method. pgs. 4 l 4, 4 l 5 [73]Assignee: Resource Data Corporation, Denver, Colo.

Primary Examiner-Archie R. Borchelt [22] Ffled' 1969 Attorney-Flehr,Hohbach, Test, Albritton & Herbert [21] Appl. No.: 795,119

[57] ABSTRACT [52] U.S. Cl ..250/83.3 UV, 250/71 R, 250/83.6 S A pulsedvisible illumination source illuminates a material to [51] Int. Cl...G0ln 21/00 allow, for p a h licopter pilot to fly over the surface of[581 p f Search 250/333 UV 33 6 S 833 7 1 the earth in darkness. Thevisible light is interrupted to allow a 1 250/833 IR; 356/151; 128/2,2,1 pulsed ultraviolet source to stimulate luminescent reradiation fromthe material which reradiation is detected by observers [56] ReferencesCited and/or cameras. Both observers and camera are shielded by gogglesor shutters so that the stimulated luminescence UNITED STATES PATENTSproduced by the ultraviolet is not masked by the visible illumination.Such shutters are synchronized with the visible illu- 2,617,945 11/1952Lord et a1. ..250/83.6 mination Pulses 3,076,l89 1/1963 Goddard..250/83.3 3,076,961 2/ l 963 Bibbero ..250/83.3 4 Claims, 2 DrawingFigures U V I2 RADIATION 49 uv SOURCES 48 AND ACTUATOR SHUTTER SW COLORF'LM x 3 i CAMERA 3 I9 1 25 27 34 32 ,24 ILLUMINATION 22 MOTOR GOGGLESSOURCES TRIGGER AMP. Q 33 SLIDE PROJECTOR MOTOR VIDEO I TONE VIDEO 46TONE ENCODER CAMERA DECODER I 16 45 SPK 43 SYNC MONITOR 4| 39 VIDEO 2336 MONITOR I I TAPE MICROPHONE 42 RECORDER CAMERA FIG..1

INVENTOR. ANDREW MADSEN B 1&4. Mafia, M I X! ATTORNEYS SYSTEM FOR DELINEATING SELECTIVE RESPONSE OF A MATERIAL TO RADIATION IN PRESENCE OFVISIBLE ILLUMINATION BACKGROUND OF THE INVENTION The present inventionis directed to a system for delineating selective response of a materialto radiation in the presence of visible illumination and moreparticularly to a system useful for geologic exploration, in the sortingof materials, and as an aid in surgery.

Airborne survey techniques, such as disclosed in U.S. Pat. No.3,043,908, entitled Fluorographic System for Aerial Survey, with thesame inventor as the present application, have been used to locate anddefine surface and subsurface mineral deposits. The subtle influence ofsuch deposits when selectively enhanced by ultraviolet radiationproduces a luminescent display of spectral signatures and patternsindicative of the types of mineral deposits present.

Both radioactivity and trace elements are one of the prime reasons forthe occurrence of luminescence. Since both factors often have anintimate relationship to intrusive rocks and hydrothermal ore bodies, itcan be expected that luminescent minerals should occur in a similarintimate relationship.

Heavy metals, as well as uranium, phosphates and rare earth elements,may be found by the above technique. Hydrocarbon deposits of certaintypes are also subject to surface fluoraphic detection.

As described in the foregoing patent, the earth's surface is surveyed bymounting a controlled source of ultraviolet radiation in an aircraftwhich then flies a specific search pattern. The luminescence orfluorescence of the earths surface caused by the ultraviolet radiationis then recorded and analyzed. I

While the above technique has proved useful, relatively high intensitiesof ultraviolet radiation are required. This is especially in view of thenecessity of operating at night and at high altitudes. Darkness isnecessary since visible illumination has a masking effect on theluminescence and/or fluorescence. Adoption of the technique in otherfields has been hindered by the darkness requirement.

OBJECT AND SUMMARY OF THE INVENTION It is a general object of theinvention to provide a system for delineating the selective response ofa material to radiation in the presence of visible illumination.

It is another object of the invention to provide a system as above whichis useful for geologic exploration, in the sorting of materials, and asan aid in surgery.

In accordance with the above objects, there is provided a system fordelineating the selective response of a material to impinging radiationfor visibly illuminating the material. The system comprises a firstsource of electromagnetic radiation directed toward the material forvisibly illuminating it. This radiation has frequencies lying within apredetermined electromagnetic frequency spectrum. A second source ofelectromagnetic radiation is directed towards the material for causingit to selectively reradiate electromagnetic energy in a spectrum whichoverlaps with said predetermined frequency spectrum or with reradiationfrom said material caused by said first source. Means are provided forintermittently interrupting the directed radiation from the first sourcetowards said material. Means are provided for receiving the selectivereradiation from the material during the interruption of the firstsource.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view in sectionof a helicopter embodying the system of the present invention andillustrating a survey of the surface of the earth.

FIG. 2 is a schematic block diagram of a system embodying the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG.1, there is shown a helicopter 10 which may be, for example, a Bell JetRanger. Mounted in a pod 11 attached to the underside of the helicopteris a first source of electromagnetic radiation which producesultravioletradiation. Pod 11 includes several luminars 12 to produce thedesired intensity of radiation. The ultraviolet radiation producesoverlapping beams and is canted 15 forward to allow a convenient spacialrelationship to a human observer 13 seated in the front of thehelicopter, film camera 14, and video camera 16.

Visible illumination of the ground terrain designated 17 is produced bya second pod 18 which has several visible illumination sources 19grouped together in aligned reflectors. These would normally be of thepulse capacitor discharge type. Helicopter 10 would normally fly in apredetermined survey pattern above the surface of the earth at altitudesof from 50 to 500 feet, depending upon the intensity of ultravioletradiation desired on the ground surface 17 and the obstacles presentnear the ground surface to thereby provide information as to thegeologic nature of surface 17.

As described more completely in the above mentioned Madsen patent, theprincipal application of the fluorographic survey technique is in thedetection of hydrocarbon compounds, such as petroleum depositsassociated with a submerged source. Since geological petroleum depositsappear to undergo diverse conditions of diffusion and migration throughpermeable faults, joints or minute fractures, principally adjacent theedges of a deposit, these discontinuities eventually exercise aninfluence on vegetation and cover soil at the earths surface. Suchinfluence is detectable as a fluorescence when radiated with ultravioletenergy. Thus, as taught by the Madsen patent, helicopter 10 would flyover the area to be surveyed while repetitively discharging pulses ofradiant energy from ultraviolet sources 12. These stimulate theluminescence of the earth's surface and such luminescence is observedeither by the camera 14, video camera 16 or observer 13. At the sametime intermittent visible illumination is provided by light pod 18.However, this illumination from source 18 is interrupted intermittentlyor at periodic intervals to allow the various recording devices of theultraviolet stimulated luminescence to function without the maskingbrightness of the visible illumination sources. The specific mode inwhich this is accomplished is more fully illustrated in FIG. 2 whichwill be discussed below.

From a broad standpoint, the undesirable masking brightness of thevisible illumination may be produced by radiation which is in thefrequency spectrum of the visible illumination itself or by reradiationfrom the material or surface caused by the visible illumination whichwould overlap with the stimulated luminescence radiation. In order toprevent this masking brightness in accordance with the present inventionthe illumination means 18 is intermittently interrupted and at the sametime the means for receiving selective reradiation from the material orthis ground surface 17 are unshuttered or unblocked to allow thestimulated luminescence to be received during periods when the radiationfrom the visible illumination sources 19 are not activated.

Referring now specifically to FIG. 2 there is illustrated the variouscomponents of the system of the present invention. The illuminationsources 19 are activated through a trigger amplifier 22 which in turn iscontrolled by a synchronizer 23 coupled to it. Synchronizer 23determines the rate at which the visible sources 19 are pulsed on andthe time period of the pulse. Factors to be considered in determiningthis rate are reducing flicker to a minimum for the pilot of theaircraft while at the same time allowing sufficient time for reradiationfrom the ground or material being stimulated by the ultravioletradiation.

Synchronizer 23 is coupled by a line 24 to an AND gate 25 whichactivates ultraviolet light sources 12 and a shutter mechanism 27 forcamera 14. The other input to AND gate 25 is provided by a DC source 28coupled to an input lead 29 through a series connected shutter actuator31. In practice the shutter actuator would be automatically operated toopen shutter switch 27 allowing the camera 14 to view the stimulatedluminescence of the ground surface and at the same time activateultraviolet sources 11 during non-illumination periods of illuminationsources 19. Thus, synchronizing pulses from synchronizer 23 would be ofa polarity during one mode such as to trigger amplifier 22 and at thesame time maintain AND gate 25 in a closed condition. In its other modethe amplifier 22 would not be triggered and the synchronizing signalwould serve as one of the coincidence inputs to gate 25 to open the gateto activate ultraviolet sources 12 and allow the shutter to film camera14 to be opened to record the stimulated luminescence of the groundsurface.

Synchronizer 23 is also coupled to shutters 32 and 33 driven by motors34 and 35 respectively. Shutter 33 shutters a video camera 16 so that itreceives light information from the ground surface only during period ofultraviolet stimulated luminescence. Shutter 32 is a representationalshowing of a shutter that would be placed over the viewing port orgoggles of the observer 13 as shown in FIG. 1. In actual practice theshutters or goggles are preferably solid state and the synchronizingpulse of synchronizer 23 would merely provide an electrical input pulseto the goggles to blank them or shutter them at the appropriate times.Such a solid state light transmission means is manufactured by MarksPolarized Corporation and is termed a VARAD (trademark) dipole cell.

The video camera 16 is also coupled through synchronizer 23 to a monitor36 which is normally mounted in the helicopter and in addition a videotape recorder 37 for recording the scenes recorded by video camera 16.Also coupled to video tape recorder 37 are a tone encoder 37 whichreceives the output of AND gate 25 and converts it into tones forproviding additional information as to the closure or shuttering of thecolor film camera 14 and activation of ultraviolet sources 12. Amicrophone 39 coupled through switching unit 41 allows the observer onthe helicopter to make oral observations. The tape recorder 37 iscoupled to a ground station via air-ground links 42 and 43 to a groundmonitor 44, a ground speaker 45, and a tone decoder 46 which serves thepurpose of synchronizing a slide projector 47.

OPERATION In operation the area to be surveyed is brightly illuminatedby illumination sources 19 allowing the pilot of the helicopter to flythe airborne platform for the equipment at a relatively low altitudeduring the night time but still with safety. The visible illuminationalthough formed of pulses of relatively short duration appears steadydue to the eyes retinal retention characteristics. However, the observer13 with the special goggles 32 and the video camera 16 will only receiveluminescence stimulated by ultraviolet sources 12. Similarly color filmcamera 14 only has its shutter open during periods of no visibleillumination.

In order to supplement ultraviolet sources 12 a continuous ultravioletradiation source 48 may be provided having a power supply 49.

Thus the helicopter operates in a brightly lighted environment and yetthe exploration system operates in necessary darkness to be effective.The observer 13 who would normally be a geologist can see and relateboth in the visible as well as the ultraviolet luminescence realm.

The above system is also more effective since the visible illuminationallows the helicopter to fly relatively close to the ground thusincreasing the intensity of ground radiation to increase the stimulatedluminescence.

Although a ground surface 17 is illustrated in FIG. 1 in combinationwith the helicopter 10 the system of the presentinvention also hasseveral other applications. For example, if a number of differentarticles are to be sorted visible illumination can be provided allowingworkers in the area adjacent the articles to function in a lightedenvironment. Radiation from the ultraviolet source can provide aselective radiation with an observer wearing the special goggles who canthen detect differences in the articles to thereby sort them. Thus, FIG.1 could be modified so that the equipment located in the helicopter 10would be in a fixed installation and the ground surface 17 wouldrepresent the plurality of articles to be sorted.

Similarly, in another application the ground surface 17 could actuallybe the operating field of a portion of the anatomy of a human beingwhere, for example, the body portion has been treated with an aerosolfluorescing medium which would cause the medium to outline points orareas of discontinuity in the body. In other words, fluid dynamics wouldcause an aerosol spray to concentrate in the discontinuities and thestimulated luminescence caused by the impinging ultraviolet radiationwould indicate to the observer-surgeon a higher intensity ofluminescence at these points. In addition, for example, where there is aforeign particle in the body this foreign particle would have adifferent degree of luminescence relative to the body itself. Forexample, a glass particle embedded in an eye of a human being. With thesystem of the present invention the attending medical personnel wouldstill be allowed to effectively function in the area adjacent thesurgery.

Thus, the present invention has provided an improved system fordelineating a selective response of a material to radiation in thepresence of visible illumination. The material may be the ground surfacefor geologic exploration, a group of articles to be sorted or anoperating field of the human body.

I claim:

1. A system for delineating the selective response of a material in adark environment to impinging ultraviolet radiation while visiblyilluminating said material comprising, a first source of electromagneticradiation including the visible range directed towards said material forvisibly illuminating said material, said radiation having frequencieslying within a predetermined electromagnetic frequency spectrum, asecond source of electromagnetic radiation including the ultravioletrange directed towards said material for causing said material toselectively reradiate electromagnetic energy in a spectrum whichoverlaps with said predetermined frequency spectrum or with reradiationfrom said material caused by said first source, means for intermittentlyinterrupting said visible radiation from said first source towards saidmaterial, and means for receiving said selective reradiation from saidmaterial during said interruptions.

2. A system as in claim 1 together with means for shuttering said meansfor receiving said selective reradiation during periods when radiationfrom said first source is being directed toward said material.

3. A system as in claim 1 in which said material includes portions ofthe earth's surface and said first and second sources are moved abovesaid surface at a predetermined altitude.

4. A system as in claim 3 in which said first and second sources areattached to an airborne platform having a human pilot and said visibleillumination allows said pilot to direct said platform.

1. A system for delineating the selective response of a material in adark environment to impinging ultraviolet radiation while visiblyilluminating said material comprising, a first source of electromagneticradiation including the visible range directed towards said material forvisibly illuminating said material, said radiation having frequencieslying within a predetermined electromagnetic frequency spectrum, asecond source of electromagnetic radiation including the ultravioletrange directed towards said material for causing said material toselectively reradiate electromagnetic energy in a spectrum whichoverlaps with said predetermined frequency spectrum or with reradiationfrom said material caused by said first source, means for intermittentlyinterrupting said visible radiation from said first source tOwards saidmaterial, and means for receiving said selective reradiation from saidmaterial during said interruptions.
 2. A system as in claim 1 togetherwith means for shuttering said means for receiving said selectivereradiation during periods when radiation from said first source isbeing directed toward said material.
 3. A system as in claim 1 in whichsaid material includes portions of the earth''s surface and said firstand second sources are moved above said surface at a predeterminedaltitude.
 4. A system as in claim 3 in which said first and secondsources are attached to an airborne platform having a human pilot andsaid visible illumination allows said pilot to direct said platform.